Category

Published on

31 Jul 2010

Abstract

This report discusses the benchmark shake table testing program on a full-scale two-story woodframe townhouse building conducted within the NEESWood Project. The test building represents the world's largest woodframe structure tested on a shake table. The size and weight of the test structure required the simultaneous use of the two tri-axial shake tables at the University at Buffalo UB-NEES site. The testing program is focusing on the various construction elements that may have significant influence on the seismic response of woodframe buildings and that should be considered in performance-based seismic design.

The benchmark test structure is based on one of the four index buildings designed within the recently completed CUREE-Caltech Woodframe Project [1]. It represents one unit of a two-story townhouse containing three units, having approximately 1800 ft^2 of living space with an attached two-car garage. The height of the townhouse from the first floor slab to the roof eaves is 18 ft and its total weight is approximately 80 kips. The exterior walls of the townhouse test building are covered on the outside with 7/8 in. thick stucco over 7/16 in. thick OSB sheathed shear walls and 1/2 in. thick gypsum wallboard on the inside.

Multiple seismic tests were conducted for various configurations of the benchmark test building. Five different seismic test phases were included in the test program. Low amplitude white noise tests were also conducted between the seismic tests of each phase to determine the variations of the dynamic characteristics of the test building as it experienced increasing levels of damage. The test structure was repaired after each test phase in an attempt to return the lateral load resisting system to its original characteristics before the start of each subsequent test phase. Note that all test phases were performed for a constant mass of the test building by incorporating ballast weights at the floor level for the test phases in which some of the wall finish materials were omitted.

Two different types of tri-axial historical ground motions were used for the seismic tests: ordinary ground motions and near-field ground motions. The ordinary ground motions represented a Design Basis Earthquake (DBE) having a probability of exceedance of 10% in 50 years (10%/50 years), or equivalently, a return period of 475 years. The near-field ground motions represented a Maximum Credible Earthquake (MCE) having a probability of exceedance of 2% in 50 years (2%/ 50 years), or a return period of 2475 years. The test structure was instrumented with nearly 230 displacement, acceleration, and force measuring devices to maximize the amount of information regarding the response of the structure during the various tests.